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Dual Density Mask for Photoresist

Publishing Venue

IBM

Related People

Hartley, PA: AUTHOR

Abstract

A tri-level mask which has transparent areas, opaque areas, and partially transparent areas can be made according to the process described below. Such a mask can be used to expose positive photoresist so that the photoresist can be first removed where one desires circuit lines and then removed where one desires lands or interconnecting areas. The process is as follows: (a) A first mask is made which is totally opaque except for the areas where one desires lines and lands. The areas where one desires lines and lands are totally transparent. (b) A second mask is made which is all clear except in the areas where one desires lands. The areas where one desires lands are made totally opaque. (c) A diazo copy is made from the second mask. This diazo copy will be completely clear except for the areas where one desires lands.

Country

United States

Language

English (United States)

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Dual Density Mask for Photoresist

A tri-level mask which has transparent areas, opaque areas, and partially
transparent areas can be made according to the process described below. Such
a mask can be used to expose positive photoresist so that the photoresist can be
first removed where one desires circuit lines and then removed where one
desires lands or interconnecting areas. The process is as follows: (a) A first
mask is made which is totally opaque except for the areas where one desires
lines and lands. The areas where one desires lines and lands are totally
transparent. (b) A second mask is made which is all clear except in the areas
where one desires lands. The areas where one desires lands are made totally
opaque. (c) A diazo copy is made from the second mask. This diazo copy will be
completely clear except for the areas where one desires lands. These areas are
partially transparent. (d) The first mask (a) and the mask made in step (c) are
matched, and these are printed onto a silver halide lithographic emulsion. The
resulting image will be transparent except that the circuit lines will be totally
opaque and the land areas will be partially transparent. The optical density of the
lands is controlled by the exposure time, other processes concerned with the
manufacture of the mask remaining the same.